The degree of degenerative changes and medial meniscal extrusion of the knee progress with increasing severity of posterior root lesions of the medial meniscus in middle age: A cross-sectional study.

Background: The aim of this study was to evaluate the relationships between radiologic features and the severity of medial meniscal posterior root (MMPR) lesions.

Methods: Patients were classified into three groups: Group I, MMPR degeneration (n = 50); Group II, partial MMPR tear (MMPRT; n = 46); and Group III, complete MMPRT (n = 54). Forty-three patients without intra-articular pathologies formed a control group. Knee radiographs were assessed for mechanical femorotibial angle, Kellgren-Lawrence grade and joint space width of the medial compartment. MRIs were assessed for MMPR-related findings, including extent of medial meniscal extrusion (MME), insertional osseous change at the MMPR attachment, cartilage status, subchondral bone marrow lesions, effusion, and osteophytes of the medial compartment.

Results: Varus degree and proportions of Kellgren-Lawrence grade 2 and 3 were higher as the severity of MMPR lesions increased (P < 0.001, respectively). Joint space width decreased as the severity of the MMPR lesion increased (P < 0.001). On MRI, MME, ratio of pathologic MME (>3 mm), the International Cartilage Research Society grade of the medial compartment, the proportions of moderate and high effusion, and proportions of grade 2 and 3 osteophytes increased as the severity of MMPR lesions increased (P < 0.001, respectively). A higher proportion of intraosseous cysts was seen in Group I than in the other groups (P < 0.001).

Conclusions: The extent of MME and ratio of pathologic MME increased as the severity of MMPR lesions increased. Radiologic features reflecting osteoarthritis worsened as the severity of MMPR lesions increased. On MRI, MMPR degeneration is significantly associated with intraosseous cyst at the MMPR insertion site.